We previously identified a second messenger-regulated signaling system in the environmental bacterium Pseudomonas fluorescens, which controls biofilm formation in response to levels of environmental inorganic phosphate. This system contains the transmembrane cyclic di-GMP (c-di-GMP) receptor LapD and the periplasmic protease LapG. LapD regulates LapG and controls the ability of this protease to process a large cell-surface adhesin protein, LapA. While LapDG orthologs can be identified in diverse bacteria, predictions of LapG substrates are sparse. Notably, the opportunistic pathogen P. aeruginosa harbors LapDG orthologs, but neither the substrate of LapG nor any associated secretion machinery has been identified to date.

 

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